The Stirling cycle engine utilizes contraction and expansion of heated and cooled inter-communicating gas volumes in timed relation to the extraction of working energy. Engines utilizing this cycle can be either of the external combustion type or of the internal combustion type. Typically those of the external combustion type should be referred to as a true Stirling type engine commensurate with the first embodiments of Rev. Stirling back in the early 1800's. When operating an internal combustion circuit, it is convenient to refer to such engine as an Ericsson type Stirling engine wherein the flow of working fluid is controlled by valves as opposed to the use of the volume changes to control flow. More simply, the regenerative thermodynamic cycle is closed in the true Stirling cycle machine and is open in the Ericsson-Stirling cycle machine. This invention is primarily concerned with an Ericsson-Stirling cycle machine.
External heating of a chamber, as required in a true Stirling engine, inherently requires substantial start-up time and necessitates the use of significant quantities of costly and limited high temperature metals, for example, nickel based alloys. Improved efficiency of heat transfer from such external heating circuit to the closed working fluid is obtained by use of a working fluid having low density and high thermal conductivity, such as hydrogen or helium. However, no convenient mass distribution means is currently available for vehicular users of these types of gases; such gases must be separately stored in the vehicle, thereby introducing additional cost factors.